1. Field of the Invention
The present invention relates to an inspecting apparatus for inspecting semiconductor wafers (hereinafter referred to simply as "wafers"). More specifically, it relates to a wafer inspecting apparatus for inspecting the electric characteristics of a wafer by bringing the contact projections (probes) into simultaneous contact with the inspecting electrodes of all semiconductor integrated circuits (hereinafter referred to as "IC chips") that are formed on the surface of a wafer.
2. Discussion of the Background
A conventional wafer inspecting apparatus (e.g., a prober) comprises the following: a cassette for storing wafers therein; a loader section for conveying the wafer between the cassette and an inspecting section; and a checking section (a prober section) for checking the electric characteristics of the wafer conveyed from the loader section. The loader section is provided with a conveyance mechanism (fork) and a sub-chuck. By the conveyance mechanism, the wafers stored in the cassette are conveyed to the loader section one by one. During the conveyance, a wafer is placed on the sub-chuck, on which it is preliminarily positioned (pre-alignment), with the orientation flat used as a reference. The prober section is provided with: a main chuck, movable in X-, Y-, Z- and .theta.-directions, for holding a wafer mounted thereon; an alignment mechanism; a probe card; and a tester. After being placed on the main chuck by the fork, a wafer is moved in the in X-, Y-, Z- and .theta.-directions by the alignment mechanism, in such a manner that the wafer is aligned with the probes. Thereafter, the wafer is index-fed in the X- and Y-directions, and the probes examine the IC chips formed on the wafer (probing). The tester has contact pins (e.g., pogo-pins) which correspond in number to the probes of the tester card. Electric signals are exchanged between the IC chips probed by the probes and the contact pins, and the tester connected to the contact pins inspects the electric characteristics of each IC chip. After the check, the wafer on the main chuck is returned into the cassette by the fork and the other wafers stored inside the cassettes are sequentially checked in a similar manner to that mentioned above.
The conventional wafer inspecting apparatus inspects the IC chips formed on a wafer one by one or in units of a predetermined number. If the wafer is large in diameter (the demand for large-diameter wafers is expected to grow in the future), a wide space is needed around the main chuck so as to enable the index feed of the wafer. Accordingly, the inspecting apparatus is inevitably large in size.
In addition to the growing demand for large-diameter wafers, there is also a demand for miniaturization for the wiring layers of the IC chips. For example, the wiring layers are required to be of the order of sub-quarter microns. Under the circumstances, the index feed must be controlled with very high accuracy.
In the conventional wafer inspecting apparatus, the main chuck is moved in the X- and Y-directions so as to index-feed the wafer. The driving mechanism for moving the main chuck inevitably produces particles, and such particles are likely to attach to the wafer. Some measures have to be taken against such particles, and taking such measures becomes more and more important in accordance with the current trend toward the miniaturization of the wiring layers.
In recent years, a new type of contactor is under development. It is designed to bring contact projections into simultaneous contact with the inspecting electrodes of all IC chips that are formed on a wafer. If such a contactor is realized, the inspection throughput could be remarkably improved. However, the realization of such a contactor does not necessarily solve the problems in the art. That is, the contact pins and wiring lines of a tester, which are connected to the contact projections that are brought into simultaneous contact with the inspecting electrodes of all IC chips, are very large in number. Roughly speaking, the number of contact pins or wiring lines which must be provided for the tester is in the range of 20,000 to 50,000. A tester presently available cannot cope with such a large number of contact pins or wiring lines; it can cope with thousands of contact pins at the most. Hence, there is an urgent demand for a wafer inspecting apparatus which can be used efficiently with a presently-available tester.